Identification of Recombinant Human Parathyroid Hormone (1–34) by Nanoelectrospray Ionization-Quadrupole Time-of-Flight Tandem Mass Spectrometry

Recombinant human PTH (1–34) was identified by electrospray ionization-quadrupole time-of-flight tandem mass spectrometry (ESI-TOF-MS). The calculated molecular weight of PTH (1–34) was 4117.76 by ESI-MS, and the measured value was 4115.21. The percent of measurement error was only 0.06%. PTH (1–34) was digested by trypsin at 37° overnight. The tryptic-digested peptides were analyzed, and then four charged peptides were selected to determine their amino acid sequence by ESI-MS/MS. Through analysis of the a, b and y series ions, the sequence of peptide m/z 728.4 determined by ESI-MS/MS was VSEIQLMHNLGK, and the database search results of the other three peptides showed that both belonged to PTH (1–34). The study proved that the primary structure of the recombinant PTH (1–34) was accurate, and there was no amino acid deletion, mutation, or modification in its expression and in the purification process of PTH. It also showed that nanoESI-MS/MS was a good method to identify protein with the advantages of high sensitivity, fast analysis, and accuracy.